log4j 2 - Change configuration at runtime for J2EE app

Question

Currently we have J2EE applications that run on WebSphere and log4j 1.x is our company's standard for Java logging. We'd like to investigate the ability to change the log4j configuration xml file at runtime so we can change to the DEBUG level, for example, when problems are identified, and return to the ERROR level once those problems are cleared up and DEBUG is no longer needed. We'd like to do all this without having to recycle the application to reread the config file.

I see that DOMConfigurator.configureandWatch() is an available method that would allow the config file to be reread at runtime. However, because it spawns a separate thread that won't be shut down when the application is shut down, it is unsafe to run in a J2EE environment.

http://logging.apache.org/log4j/1.2/faq.html#a3.6

Does anyone know if this was fixed in log4 2? I haven't found anything definitive yet from the documentation and was curious if it is safe to change the config file at runtime in J2EE.

Answer 1

Re-reading the configuration file is not something you want to do in production. It means that you're changing resources which many app servers don't expect to change. Development environments can get away with it on the grounds that blowing up the app server isn't a big deal. It also means that your app might behave differently if it has to be restarted.

You're going to want to change the log levels programmatically. You can do this by using LogManager.getLogger() for the packages you care about. Once you have the logger, change the level to debug, and change it back when you are done.